The most complex process in the combustion field is the waste-to-energy process. This is due to heterogeneous nature of the feeds, whose BTU value can vary substantially, in spite of the efforts expended by designers and operators to effectively mix the feed.
As a result, first pass temperatures (at some locations) can reach 1,800° to 1,900°F, promoting high temperature corrosion and erosion.
This paper will discuss flame quenching by means of injecting fine water droplets into the center of the flame (adiabatic region). This practice has the potential to reduce and control the furnace temperature (ten (10) gallons of water takes away 170,000 BTU). The potential benefits of flame quenching to be discussed will include the following:
• Increasing combustion gas turbulence by a sudden increase in water volume of 1,670 times (water to steam);
• Reductions in CO and VOCs due to better combustion gases mixing;
• Reductions in combustion velocities and tube erosion rate;
• Reductions in NOx by lowering flame temperature; and
• The generation of new revenues by utilizing moderately contaminated wastewater or groundwater contaminated from industrial sites.
Potential disadvantages of flame quenching to be discussed will include the following:
• Possible loss of revenue due to the loss of BTUs; and
• Development of slag due to large water droplet sizes or high water velocities.